linux-kernel - Re: [PATCH ftrace/core v6 2/5] ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict

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Message-ID: <20141121144316.22459f7e@gandalf.local.home>
Date:	Fri, 21 Nov 2014 14:43:16 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Seth Jennings <sjenning@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Petr Mladek <pmladek@...e.cz>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Namhyung Kim <namhyung@...nel.org>,
	Miroslav Benes <mbenes@...e.cz>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH ftrace/core v6 2/5] ftrace, kprobes: Support IPMODIFY
 flag to find IP modify conflict

On Fri, 21 Nov 2014 13:05:29 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Fri, 21 Nov 2014 05:25:16 -0500
> Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:

> > + * IPMODIFY - The ops can modify the IP register. This can only be set with
> > + *            SAVE_REGS. If another ops is already registered for any of the
> > + *            functions that this ops will be registered for, then this ops
> > + *            will fail to register or set_filter_ip.
> 
> It's blocked by any ops sharing the same function, or just another ops
> with this flag set? The comment doesn't specify. The code looks like
> the latter.

I applied it and gave it the following updates to comments:

-- Steve

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 93cf0478f64e..ed501953f0b2 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -107,9 +107,9 @@ ftrace_func_t ftrace_ops_get_func(struct ftrace_ops *ops);
  *            in such cases the arch must not modify it. Only the arch ftrace
  *            core code should set this flag.
  * IPMODIFY - The ops can modify the IP register. This can only be set with
- *            SAVE_REGS. If another ops is already registered for any of the
- *            functions that this ops will be registered for, then this ops
- *            will fail to register or set_filter_ip.
+ *            SAVE_REGS. If another ops with this flag set is already registered
+ *            for any of the functions that this ops will be registered for, then
+ *            this ops will fail to register or set_filter_ip.
  */
 enum {
 	FTRACE_OPS_FL_ENABLED			= 1 << 0,
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 531e72a716c3..929a733d302e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1810,8 +1810,8 @@ static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
 		return 0;
 
 	/*
-	 * Since the IPMODIFY is very address sensitive action, we do not allow
-	 * ftrace_ops to set all functions to new hash.
+	 * Since the IPMODIFY is a very address sensitive action, we do not
+	 * allow ftrace_ops to set all functions to new hash.
 	 */
 	if (!new_hash || !old_hash)
 		return -EINVAL;
--
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